1. Field
Exemplary embodiments of the present invention relate to a nonvolatile memory device, and more particularly, to a three-dimensional (3D) nonvolatile memory device including a plurality of memory cells that are vertically stacked over a substrate.
2. Description of the Related Art
A nonvolatile memory device refers to a memory device that maintains stored data even though a power supply is off. A variety of nonvolatile memory devices, for example, a flash memory and so on, may be used.
Meanwhile, a two-dimensional (2D) memory device, which is formed as a single layer over a silicon substrate, may reach a limit in integration degree, and a 3D non-volatile memory device including a plurality of memory cells stacked vertically over a silicon substrate may be implemented to further increase the integration degree.
FIG. 1 is a cross-sectional view illustrating a conventional 3D non-volatile memory device.
Referring to FIG. 1, a pipe gate electrode 11 and a plurality of interlayer dielectric layers 12 and gate electrode layers 13, which are alternately stacked, are formed over a substrate (not illustrated).
A pair of channel holes is formed through the interlayer dielectric layers 12 and gate electrode layers 13. The pipe gate electrode 11 includes pipe channel holes formed therein, and the pipe channel holes couple the pair of channel holes.
A memory layer 14, a channel layer 15, and a dielectric layer 16 are sequentially formed in the channel holes and the pipe channel holes.
Meanwhile, a first trench T1 is formed between the pair of channel holes to isolate the gate electrode layers 13 for each channel hole. Furthermore, a second trench T2 is formed between channel holes, which are adjacent to each other while respectively belonging to different pairs, and isolates the gate electrode layers 13 for each string.
According to the conventional nonvolatile memory device, since the plurality of memory cells are vertically stacked, a vertical height increases. Also, the horizontal width of the uppermost parts of the channel holes or the trenches inevitably increases.
Specifically, although FIG. 1 illustrates that the channel holes or the trenches have a constant width, the width inevitably decreases from the upper part toward the lower part of the channel holes or the trenches due to a characteristic of an etching process. Therefore, when the vertical height of a nonvolatile memory device is increased, the horizontal width of the uppermost parts of channel holes or trenches should be increased. Accordingly, the horizontal area of the nonvolatile memory device inevitably increases. Thus, a structure capable of preventing the horizontal area from increasing is useful.